The Plate 77 Penny Red, one of only five in the world, including one at the British Museum, was bought by a private collector for £495,000.

The new owner, who did not want to be named, said: "I am so pleased I bought this stamp, it has given me a buzz I really didn't expect.

"I am sure it will prove to be a fabulous investment and, in an uncertain financial world, will prove its worth."

Keith Heddle, of collectibles merchant Stanley Gibbons, which sold the stamp, said: "This is one of the most desirable and iconic of British stamps for collectors worldwide, highly sought after for more than 100 years. I'm delighted this one has found a home in Britain."